A circuit breaker is used to protect an electric circuit from damage caused by a persistent overcurrent condition, short circuit, fault or other malfunction. FIG. 1 generally depicts an exemplary three phase circuit breaker 1. The circuit breaker 1 includes a handle 3 that extends from a housing 5 that is molded from an insulating material. The handle 3 is moveable between on, off and tripped positions to enable an operating mechanism located in the housing 5 to engage and disengage a moveable contact and a stationary contact for each of the three phases in a well-known manner, such that a line terminal 7 and load terminal 9 of each phase are electrically connected.
The line 7 and load 9 terminals of the circuit breaker 1 are connected to associated wires of the electric circuit by a connector or lug. One type of lug includes a lug body having a conductor hole for receiving a conductor portion of a wire and a threaded hole that is perpendicular to the conductor hole. The lug further includes a lug screw that is threadably engaged with the threaded hole to form a lug assembly. In order to connect a wire to the circuit breaker, an installer strips an end of wire insulation to expose a conductor. The conductor is then inserted into the conductor hole such that, when the installer tightens the lug screw, the body of the screw enters the conductor hole and contacts the conductor. The lug screw is then tightened to compress the conductor against the terminal and to prevent the conductor from being pulled from the lug assembly during normal use.
Circuit breakers are typically shipped from the factory with one or more lug assemblies that are to be used by an installer at a work site, for example, to connect a circuit breaker to wires of an electric circuit. It is desirable to hold the lugs in a set-up position on the terminals so that they are readily accessible to an installer so as to reduce assembly time. A threaded fastener element may be used to attach a lug to a terminal of a circuit breaker. A disadvantage with this arrangement is that a tool such as a conventional screwdriver, or a pneumatic, electric or hydraulic screwdriver, must be used to tighten the fastener element. In addition, a calibrated torque wrench is needed as part of a quality assurance check to ensure that a desired torque value has been applied to the fastener element. Alternatively, the lug may be molded into the housing of a circuit breaker. A disadvantage with this arrangement is that the lug is not removable from the housing. Therefore, if the lug screw is damaged for example, the entire circuit breaker must be replaced since the lug cannot be removed from the housing.